Conventionally, as to electronic apparatuses structured to have a printed-circuit board attached parallel to a gravitation direction in such a way as to divide the inner space, in the case where the casings of the electronic apparatuses are to be arranged in parallel with side walls of adjacent casings in contact and extending in a direction parallel to the printed-circuit board, the electronic apparatus has been structured to dissipate heat inside the electronic apparatus by convection and ventilation of air through vents provided in the upper and lower surfaces of the casing.
For example, according to Patent Literature 1, for a system in which the casings are arranged in parallel with their side walls in contact, there is a measure where the casing has a vent in communication with an adjacent casing, and outside air is supplied through this vent to the inside of the casing.
Further, according to Patent Literature 2, there is a measure where a vent is provided downwind of one of spaces partitioned by a wall in the same casing and where air in one of the spaces is discharged by negative pressure action into the other space, thereby obtaining a cooling effect.